| When choosing a home alarm system, there are a | | | | any moving object that enters the protected space |
| number of factors that you should consider before | | | | changes the frequency of the surrounding sound |
| making the final purchase. Probably on the top of | | | | waves. This shift triggers the home alarm system. |
| your list of considerations is alarm type. However, | | | | Microwave Detectors |
| you also have to decide on what type of sensors | | | | These function in a similar manner to ultrasonic |
| you want to install. Sensors are the most vital | | | | detectors, but instead of using sound waves, they |
| component of your home alarm system. These will | | | | use high frequency radio waves. These can go |
| detect any intrusions on your property. Here is a list | | | | through walls, unlike ultrasonic waves. |
| of the most common sensors on the market. | | | | Magnetic Switches |
| Passive Infrared Motion Detector | | | | These are generally used for protecting windows and |
| PIR sensors are one of the most common detectors | | | | doors. They are a popular choice due to their |
| used in home alarm systems due to their affordability | | | | affordability, durability and ease of use. Homeowners |
| and practicality. The term passive refers to the fact | | | | can easily install them themselves; they consist of |
| that these sensors function without the need to | | | | two separate parts, the magnet and the switch. The |
| generate and radiate their own energy. These types | | | | swich contains a spring which when closed, creates |
| of home alarm systems are able to detect body | | | | an electrical circuit with the magnet. If a door or |
| heat, or rather changes in the ambient temperature. | | | | window is opened the circuit breaks, thus triggering |
| If the PIR detects a temperature spike caused by | | | | the alarm. |
| the presence of a foreign object or intruder, it will be | | | | Glass Break Detectors |
| set off. However, the alarm is usually set on a delay, | | | | The sound of glass breaking occurs in a wide band of |
| allowing the sensors to differentiate between | | | | frequencies-from infrasonic which humans cannot |
| temperature zones in order to determine if there is | | | | hear, to ultrasonic, which is indeed audible to humans. |
| actually an intruder. This delay also allows the | | | | Glass break detectors are installed next to glass |
| homeowner to deactivate the alarm in the event of | | | | panes and are set off when glass breaks. |
| a false positive. As infrared energy doesn't pass | | | | Photoelectric Beams |
| through glass, passers-by cannot accidentally trigger | | | | These detect the presence of an intruder using infra |
| the alarm. | | | | red light beams, which are usually stacked in rows of |
| Ultrasonic Detectors | | | | two or more. If anyone obstructs a beam, the home |
| These sensors utilize high frequency sound waves to | | | | alarm system will go off. |
| detect movement within a confined area. Frequencies | | | | Vibration Sensors |
| inaudible to human ears, between 25 kHz and 75 kHz, | | | | These devices are mounted on some sort of barrier, |
| are transmitted and bounced off the walls, furniture, | | | | such as a fence, and detect vibrations. The sensors |
| and ceiling in a protected room. Using the Doppler | | | | can be tuned to sense different levels of vibration, |
| shift principle, the sensor is able to detect movement | | | | which is especially useful in avoiding false alarms |
| as a result of any shifts of the stabilized frequency; | | | | caused by animals or wind disturbances. |